Oil leak from cyclinder area ('68)

[wkrtsm]

About 10 years ago, I had large juggs installed, rods, rod bearings, webers, cam. The valves were not replaced. Since then, the car has only been driven several miles maybe once every 1-2 months. Started noticing that after driving, there was oil on the left header. When on the freeway can see a thin oil smoke trail at maybe 70-80 MPH but not at e.g. 55. (this is likely from greater oil pressures at higher RPMs).

Talked with my mechanic and he said it was probably not a burnt exhaust valve. My thinking is that it's probably a leaking seal for the rod cover tube for one of the cylinders, since I know those were never replaced and they are rubber.

Since i need to replace the clutch, I thought i would pull the engine (can do this in 5 minutes), remove shrouding, pressure wash the external cylinder juggs and block, weld together an engine frame, run the gas line and battery, start, let idle and maybe slow revs (so the engine stand doesn't flip), then watch where the oil accumulates from. My mechanic said he could just pressure wash the engine, put it up on a hoist and determine where/how the oil is leaking.

Any guesses as to what the greatest probability is for causing this leak?

[JK McDonald]

Hey Wkrtsm - Just a comment - I'm no expert on the 912 but I have rebuilt multiple air cooled 911 engines. Since the assembly procedure of the case, cylinders and heads are related perhaps you might get away with just re-torquing your cylinder heads. Also you could try the "Red - RTV Silicone Gasket Maker" on the valve cover gaskets and (after market - expandable) push rod tubes. I know some owners cringe at applying RTV anywhere on a Porsche but - if you are very careful and use it sparingly - it does the job in limited places.

If that doesn't remedy the oil seepage, and you decide to reseat the cylinders and install new copper gaskets, I have had excellent long term results using the highly recommended "Loctite 574" imported from Germany. Although this stuff is priced like liquid gold - it has the best of everything in long term strength, flexibility and sealing characteristics needed for the fluctuating temp range of air cooled engines. I have used it successfully on Frau Helga, Well Hung and Ol' Blue -

Good Luck - Michael

[wkrtsm]

Thanks, you mentioned reseating the heads on the cylinder juggs, not reseating the juggs on the block? My mechanic said the cylinder to block seals can go as well. I dont think I've blown a head gasket as you can hear those. The idle and higher revs is basically pretty quiet regarding lifters, etc.

It's probably the valve cover gasket, push rod cover seal, or oil cooler gasket. But I do need a clutch so I'll pull the engine tomorrow anyhow.

[JK McDonald]

Hey Wkrtsm - Sorry for not making my suggestion clear There is a copper ring (gasket) between the cylinder base and the case which could be one source of your oil seepage. To replace these copper gaskets you remove the heads, lift the cylinders off the pistons and then reseat everything during reassembly + "Loctite 574".

The "deck height" or component stack is important to be matched on each side of the motor. This is a combination of :

1 Matched machined surface depth at the case - under each cylinder base
2 Matched thickness of the cylinder base copper gaskets -
3 Matched end to end length of the cylinders -
4 Matched each machined recess surface inside head - Cylinder head mating area

Naturally the 912 cylinder deck height stack (2 cylinders per side) would not be as critical as the 911 (3 cylinders per side) but - you would want both your cylinder and head combinations to be as square to each other as possible. On your application - you mentioned installing over sized cylinders which would put additional stress on trying to keep a tight oil seal at the case/cylinder point of contact. On the 912 - perhaps shimming the deck height (base of a slightly mismatched cylinder) using multiple copper gaskets can be used ?

Good Luck - Michael

[wkrtsm]

Pulled the engine and transaxle last night, a lot of oil where the two header pipes meet below the oil pump. Also quite a bit oil all over the case near the starter. Will separate the transmission from the engine and mount on stand today, degrease and pressure wash, hookup electrical lines, battery, start switch, and gas line/tank, and then start and watch for oil leakage to troubleshoot.

[wkrtsm]

So I started the engine with the transaxle bolted to the case, and the engine sitting on blocks and cable-fastened both sides of the rear engine mount bar to the lower legs of the engine crane, and cable -fastened the headers to the legs as well. First, however, here's what you have to do to wire the engine on the stand so that it runs:

1. Purchase from local auto parts store: two heavy battery cables with lead-post fasteners, a push-button switch, an on-off switch, a small gas can, and two feet of 1/4" fuel line.

2. Once you're back in the garage/shop, pull battery from car, and run heavy battery cable from battery negative and bolt to woven metal ground on transaxle case (this grounding lead is unbolted when you pull the engine)

3. Run other heavy battery cable from battery positive to large positive post on starter.

4. Run small wire from battery positive to one of the posts on the on-off switch. On the other post of the on-off switch, run 2 wires to (a) push-button switch and (b) positive terminal on coil.

5. On the push button switch, you already have a positive coming from the on-off switch, so wire the other terminal on the push button to go to the small positive lead on the starter.

6. Hook up the fuel line to the fuel filter that goes to the engine, fasten, and then simply drop the free end of the fuel line into the gas can (with gasoline in it).

7. Make sure the engine is bolted on a stand or cable-fastened to the legs of an e.g. engine crane.

8. Start the engine and voila!


I actually have two spal fans on a mocal oil cooler with a 180F thermostat, so that was just wired to the on-off switch (positive). I started the engine, let it run for about 10 minutes and held the RPM near 2000 for a while. After that I revved the engine up near 3-4000 intermittently, and noticed a heavy oil flow streaming down the front of the case immediately below the transaxle interface. In addition, when I gunned the engine oil drops were being blown out of the clutch lever hole on the transaxle. There was no oil dropping from the cylinders onto the floor or headers, or from the valve covers. There was also no oil leaking from the NPT fittings of the oil lines that go to the oil thermostat. No oil leaks from heads, timing cover, or back end near the timing pulley, or anywhere on the block on the timing cover side.

My gut feeling is that the front seal of the crank is leaking, since when I gunned the engine after 10 minutes of 2000 RPM, a lot of oil was blowing out of the clutch lever hole on the transaxle, and also flowing down the front bottom of the case below the center of the interface where the transaxle connects. Thus oil was blowing into the flywheel, clutch assembly inside the transaxle.

Also, the clutch felt like it was slipping the past few months when slightly gunning the engine in third or forth gear at 50-60 MPH when on the freeway. Dah, the clutch was probably caked in oil!!!! Also, when I pulled the engine, the transaxle and starter was covered in fresh oily black grime.

Was thinking about the oil cooler leaking, but couldn't see it because the shrouding was still on the engine. But there was no oil on the top of the case below the front shroud, and that's where it sits. So if the oil cooler was leaking, oil would be on the top of the case below the front edge of the cooling shroud.

I think the front crank seal is leaking badly, and that's why a lot of oil drops blow out of the clutch lever hole on the transaxle and leak down the center (only) of the case immediately below the interface with the transaxle.

Questions:

-Should I purchase the half-ring starter adapter, remove the transaxle, clutch assembly leaving only the flywheel, then install the engine stand yoke and starter, mount on engine stand, and then start and look though the center of the flywheel at run-time to confirm the oil is coming from the front seal?

-Or can the oil be from somewhere else, like the cooler? (i doubt it)

[wkrtsm]

One more image, no oil on timing cover side of case, etc.

[wkrtsm]

Just got done removing the transaxle, and there was oil all over the flywheel nut:



Didn't I say above that the clutch was slipping when I gunned the throttle in third gear at 50 MPH. I wonder why??????



After removing the flywheel, there's a shattered thin aluminum washer/spacer that was chewed up, and probably what cut up the green seal:



I noticed that when at 70-80 on freeway, I was really blowing oil all over the headers where they join from both sides right below the lower crank pulley in back, creating more smoke -- but less at 50 MPH. With greater oil pressures at higher RPMs, this seal break is enough to let oil flow right into the transaxle:




Questions:

1. how does the green seal come out? Just a large screwdriver?

2. Should there be oil in this area beneath the flywheel nut? Is the green seal really an oil seal, and there is supposed to be oil in this area?

3. If I replace the seal, is that the appropriate way to stop oil leaking into the clutch assembly?

4. Do I need to pull the crank, and replace a front crank oil seal?

[Jerry1]

Hi wkrtsm
You do not have to take apart your engine. If you remove the seal there is a shim if it is not there you will have oil on your clutch. If it is there then you may have to much end play on you flywheel. The slinger washer come in different thickness if there is to much play it will not seal and you will leak oil.
Here is what I use to check and install my flywheels.
Flywheel / Clutch Plate

1. Clean crank and check flywheel pins
2. Check end play
3. Install original end play shim, soft iron gasket
4. Apply grease to original gland nut
5. Install flywheel original gland nut and washer
6. Tighten to 250 lbs
7. Check end play .14 - .17mm or (.0055 – .0067in) limit .22 mm max.
push the flywheel in set gage to 0 and pull out to get your measurement.

8. Adjust shim as needed to get proper end play.
9. Clean crank, shim,
10. Install shim with a dab of US lube on both sides.
11. Install new iron gasket
12. Install flywheel seal. Lightly oil seal
13. Install flywheel, lightly oil hub
14. Apply grease to new gland nut
15. Install gland nut and washer torque to 253lbs – 271lbs
16. Check end play

Best of luck
Jerry

[Prsh356]

Most of the problem starts with the main seal and all the smoke at 60 is probably hitting the bottom of your muffler as it blows off the back of the case when you're all done go to a do it yourself car wash and blast the underside of your motor and see if you got it !

[wkrtsm]

@Jerry1 - thanks for the specs and steps - very helpful. @Prsh356, yes, the oil was hitting the headers when cruising. Indeed, i need to pressure wash the transaxle and lower case.

If the green oil seal is not OEM, it means that the Porsche mechanic who installed the big bore kit and cam, replaced it when I had those put in (I can't remember everything he did that didn't involve big bore or camshaft). The end play is the key for that oil seal, since if the end play is too large the flywheel will chew up the seal.

[Prsh356]

Since you have the motor out you may want to replace oil cooler seals .

[wkrtsm]

That's a good point - thanks. The oil cooler is under the fan shroud, and I was planning on pulling all the engine tin anyhow, including valve covers, intake manifolds, generator stand, oil filler neck, oil filler tank, oil cap, dipstick, coil bracket, generator band, throttle arms, and blast most of those parts (crushed glass to remove paint or oxide layer). Once blasted, the engine tin, valve covers, oil filler tank can go directly to powder coating. Whereas the aluminum intake manifolds, aluminum generator stand, generator band, aluminum oil filler neck, throttle arms, coil bracket, oil cap etc. can be polished with glass bead blasting.